CN114799491A

CN114799491A - Laser machining head with aperture for increasing the scan field of a laser beam

Info

Publication number: CN114799491A
Application number: CN202210092521.9A
Authority: CN
Inventors: R·莫泽; T·瓦尔德
Original assignee: Precitec GmbH and Co KG
Current assignee: Precitec GmbH and Co KG
Priority date: 2021-01-28
Filing date: 2022-01-26
Publication date: 2022-07-29
Also published as: EP4035820A1; US20220234137A1

Abstract

The invention provides a laser processing head (1). The laser processing head comprises a laser entry module (40) for introducing a laser beam (9); a collimation module (44) for collimating the laser beam; a scanning module (46) for deflecting the laser beam; a focusing module (50) for focusing the laser beam; at least one aperture (100) for limiting the diameter or cross-sectional area of the laser beam passing through the aperture to increase the scan field of the laser beam. The diaphragm includes a diaphragm body (104) and an opening (102), and is configured to restrict a cross-sectional area of the laser beam by the diaphragm body. At least one aperture is located optically downstream of the laser entry module and optically upstream of the focusing module. The invention also provides a laser machining system (2) comprising the laser machining head. Further, a method for increasing a scan field of a laser beam is provided.

Description

Laser machining head with aperture for increasing the scan field of a laser beam

Technical Field

The present invention relates generally to a laser processing head, and more particularly to a technique for increasing a scan field of a laser beam in a laser processing head.

Background

In recent years, laser processing apparatuses, i.e., apparatuses using laser beams, are increasingly applied to different industries, and various manufacturing apparatuses using laser beams, for example, are widely used in the manufacturing industry. Such laser processing apparatuses perform various techniques, such as cutting, machining, engraving, and the like, using a laser beam generated by a laser source and directed toward a target or workpiece. While being transmitted from the laser source to the workpiece or target, the laser beam typically needs to be optically altered by using different optical elements, for example focused to the workpiece by a focusing lens.

Such laser machining apparatuses usually have a component called a head, hereinafter also referred to as a laser machining head, for example a laser cutting head or a laser welding head, which faces the workpiece during application of the laser beam. During laser machining using a laser machining head, it may be necessary to reposition the laser beam from one location to which it is directed or focused to another location to which it is directed or focused. Such repositioning is typically accomplished by a scanner-based system, such as a laser scanning module, by which the laser beam may be deflected and positioned, such as an arrangement of rotatable mirrors. However, when the laser beam is deflected, it no longer propagates along the optical axis, but is incident at an angle to the focusing optics. Therefore, special laser focusing modules, such as F-Theta lenses or telecentric F-Theta lenses, may be required. The optical elements or lenses of the laser focusing module must be large compared to other optics to allow large deflection of the laser beam to achieve a large scan field. Generally, there are two factors that limit the maximum possible or allowable scan field in a system with a laser focusing module, such as a system with an F-Theta lens. First, as the deflection angle increases, it becomes more difficult to obtain a focal point whose size remains almost the same throughout the entire scan field, so that the power density distribution of the laser beam in the processing plane cannot be kept constant. Secondly, large deflection angles can cause vignetting of the laser beam at the edges of the optical elements or lenses, particularly at the "corners" of the scan field. This is especially problematic at high laser powers, since not only is power lost in the machining plane, but lost energy may also be deposited in the lens, which can lead to heating. Heating of the lens often results in a thermal focus shift, which produces an axial change in focus position. In the worst case, the lens may be damaged. For this reason, the maximum available scan field must generally be limited, in particular at high laser powers in the kW range, in order to keep the vignetting and the power losses small.

A typical scanner or laser scanning module for beam deflection may cause the laser beam to impinge on the edges of optical elements, such as the edges of a focusing lens and adjacent structures, such as a lens holder. For example, some laser scanning modules have two galvanometer motors, with one mirror for adjusting the x-direction of the laser beam and the other mirror for adjusting the y-direction of the laser beam. The two mirrors are at different distances from the focusing module, e.g., an F-theta lens. Thus, if the deflection angles of the two mirrors are the same, the beam in the direction defined by the farther mirror will hit the edge of the F-Theta lens and thus the lens edge earlier. For this reason, a limited field in the form of an ellipse can generally be used. The minor half axis is defined by the more distant mirror and the major half axis is defined by the mirror that is closer to the scanning module. When using a two-dimensional galvano scanner with one mirror that can be rotated around two perpendicular axes, the allowed scan field has a circular shape. To simplify the user's handling, the scan field is usually limited to a rectangle or square, for example by software or a control unit. Especially for square shapes, it is possible to operate independently of the orientation of the system. However, this further limits the available scan field. The problem of the laser beam striking the edges and adjacent structures of the optical element through which the laser beam passes may also occur in laser processing heads using laser scanning modules other than two galvanometer motors based on scanning mirrors, or in laser processing heads using focusing modules other than modules containing F-theta lenses. To avoid the laser beam hitting the edge, the allowable or usable scan field is limited. In addition, to make it easier for a user to use, the fields are typically displayed as rectangles and/or squares, thereby further limiting the available fields.

Disclosure of Invention

There is therefore a need for a laser processing head with a technique or mechanism for increasing the scan field of the laser beam which at least partially obviates one or more of the above-mentioned disadvantages. In particular, it is an object of the present disclosure to provide a laser processing head, and a laser processing system comprising the laser processing head, which allow to increase the scan field of the laser beam. Furthermore, it is an object of the invention to provide a method which enables an increase of the scan field of the laser beam of the laser processing head.

One or more of the above objects are achieved by the subject matter of the independent claims. Advantageous embodiments are provided in the dependent claims.

The invention is based on the idea that the scan field can be increased by reducing the diameter of the laser beam, in particular by cutting the outer peripheral part or edge of the laser beam using an aperture. Since a typical laser beam has an approximately gaussian intensity distribution, the intensity at the beam edge is typically too small to contribute to laser processing, but still has a high enough intensity to limit the allowable or usable scan field.

In a first aspect of the present technique, a laser processing head is provided. The laser processing head comprises a laser entry module for introducing a laser beam; a collimating module for collimating the laser beam; a scanning module for deflecting the laser beam; a focusing module for focusing the laser beam; at least one aperture for limiting the diameter or cross-sectional area of the laser beam passing through the aperture to increase the scan field of the laser beam. The diaphragm includes a diaphragm body and an opening. Thus, the aperture may be configured to limit the cross-sectional area of the laser beam by the aperture body, in other words by allowing a first portion of the cross-sectional area of the laser beam to pass through the opening while a second portion of the cross-sectional area of the laser beam is blocked by the aperture body. At least one aperture is located between the laser entry module and the focusing module. In other words, the at least one aperture is located optically downstream of the laser entry module and optically upstream of the focusing module. The laser entry module may represent a location or structure at the laser processing head for coupling a laser beam into the laser processing head, such as a fiber optic coupler or the like.

The phrases "optically upstream", "upstream direction", "optically downstream", "downstream direction", and the like may be understood with reference to the direction of propagation or path of travel of the laser beam from the laser entry module to the focusing module.

The focusing module may comprise at least one focusing optical element, e.g. one or more focusing lenses.

The collimating module may comprise at least one collimating optical element, e.g. one or more collimating lenses.

The scanning module may include at least one scanning optical element, such as one or more scanning mirrors. The scanning module may be a 1D or 2D scanning module configured to dynamically change the focal position of the laser beam, or may also be a 3D scanning module, e.g., a module comprising one or more movable lenses.

The focusing optics and/or the collimating optics and/or the scanning optics may generally be referred to as optical elements.

The at least one aperture may be positioned, for example, with respect to the focusing module or the collimating module or the scanning module, such that the entire cross-sectional area of the laser beam passing through the aperture opening, or a boundary or edge or periphery or circumference of the entire cross-sectional area of the laser beam, is incident, i.e. transmitted or reflected, to the optical surface of the optical element.

In other words, the aperture may be configured, e.g. dimensioned and/or positioned, within the laser processing head such that the laser beam passing through the opening of the aperture has a cross-section limited by the aperture body and the cross-section of the laser beam so limited has a boundary or edge or periphery which is fully incident on the optical surface of the optical element. In short, the portion of the laser beam that passes through the aperture can be prevented from falling outside the optical surface of the optical element, for example, to a holder, such as a lens holder or a spectacle frame, in which the optical element can be placed.

The aperture body may block the entire edge, e.g. the entire circumference or the entire periphery or the entire border, of the laser beam. For example, the portion of the laser beam that is blocked by the aperture body may have a continuous or complete or regular or symmetrical ring shape. For this purpose, the diaphragm, in particular the opening of the diaphragm, can be arranged coaxially with the optical axis of the laser processing head and/or with the optical axis of the optical element or with the beam propagation direction.

The aperture body may block only a portion of the entire edge of the laser beam. For example, the portion of the laser beam that is blocked by the aperture body may have an open or incomplete or irregular or asymmetric ring or sickle shape, or may be shaped as a segment, such as a circular arc segment, of the cross-sectional shape or area of the laser beam.

The aperture may be configured such that the second portion of the laser beam may completely or partially surround the first portion of the laser beam. The aperture may be configured such that the second portion may extend continuously along the entire periphery or edge or periphery of the laser beam, or may extend only along the entire periphery or edge or part of the periphery of the laser beam.

The aperture of the diaphragm may be smaller than the aperture of the optical surface or optical element, for example smaller than the aperture of the focusing lens or collimating lens. The term "aperture" may be understood as an opening of an optical element through which light or a laser beam passes. In particular, the diameter of the opening of the diaphragm may be smaller than the diameter of the optical surface or the aperture of the optical element.

The at least one aperture may comprise a first aperture arranged in a first position, i.e. between the laser entry module and the collimation module. The first aperture may limit a cross-sectional area of a laser beam propagating from the laser entry module to the collimating module.

The at least one aperture may comprise a second aperture, the second aperture being arranged in the second position, i.e. between the collimating module and the scanning module. The second aperture may limit a cross-sectional area of the laser beam propagating from the collimating module to the scanning module.

The at least one aperture may comprise a third aperture, the third aperture being arranged at a third position, i.e. between the scanning module and the focusing module. The third aperture may limit a cross-sectional area of the laser beam propagating from the scanning module to the focusing module.

The opening of the first diaphragm and/or the opening of the second diaphragm may have a circular shape.

The opening of the third diaphragm may have one of a circular shape, an elliptical shape, and a rectangular shape. The shape of the opening of the third aperture may mimic or correspond to the shape of the allowable or usable scan field.

The cross-sectional area or diameter of the opening of the third aperture may be configured to be smaller than the cross-sectional area or diameter of the opening of the second aperture and/or the first aperture.

The cross-sectional area or diameter of the opening of the second aperture may be smaller than the cross-sectional area or diameter of the opening of the first aperture.

The at least one aperture may comprise a plurality of apertures. The apertures of the plurality of apertures may be arranged such that a cross-sectional area or diameter of an opening of the aperture decreases from optically upstream to optically downstream. The apertures of the plurality of apertures may be arranged in one or more of the first position, the second position, and the third position. In other words, the first location may have multiple apertures, and/or the second location may have multiple apertures, and/or the third location may have multiple apertures, and/or the first location, the second location, and the third location may together have multiple apertures, each location having one or more apertures.

The cross-sectional area or diameter of the opening of one aperture may be smaller than the cross-sectional area or diameter of the opening of another aperture that is optically upstream of the one aperture.

The at least one aperture may be configured such that the width of the laser beam passing through the aperture is less than the width of the laser beam received at the at least one aperture, e.g. corresponding to 1/e of the width of the laser beam incident on the aperture ² Or in other words, the radius of the laser beam passing through the aperture may be smaller than the radius of the laser beam incident on the aperture, for example, 1/e of the radius of the laser beam incident on the aperture ² . The laser beam may be a gaussian distributed beam or may be a laser beam having an intensity distribution with a substantially gaussian distribution shape. Alternatively, the laser beam may have a top hat or annular intensity profile.

The at least one aperture may be configured such that the intensity of the laser beam exiting optically downstream thereof is less than the total intensity of the laser beam received at the at least one aperture, for example between 75% and 90%, preferably between 85% and 87%, more preferably about 86.5% of the total intensity of the laser beam received at the at least one aperture.

The cross-sectional area or diameter of the apertures of the first, second and third apertures may be such that the intensity of the laser beam exiting the most downstream aperture is less than the total intensity of the laser beam received at the at least one aperture, for example between 75% and 90%, preferably between 85% and 87%, more preferably about 86.5% of the total intensity of the laser beam received at the most upstream aperture.

The cross-sectional area or diameter of the apertures of the plurality of apertures may be configured such that the intensity of the laser beam exiting the most downstream located aperture is less than the total intensity of the laser beam received at the at least one aperture, for example between 75% and 90%, preferably between 85% and 87%, more preferably about 86.5% of the total intensity of the laser beam received at the most upstream located aperture.

The at least one aperture may be configured to adjustably or variably restrict a cross-sectional area of the laser beam, e.g., a cross-sectional area of the first portion of the laser beam, passing through the aperture. This may be performed manually or automatically. In this way, the limitation of the cross-sectional area of the laser beam can be variable or switchable, for example, depending on the application of the laser machining. The at least one aperture may be switchable between a configuration in which the cross-sectional area of the laser beam is restricted and a configuration in which the cross-sectional area of the laser beam is not restricted. Therefore, the cross-sectional area of the laser beam can also be kept constant.

The at least one aperture may be configured to vary or adjust a cross-sectional area of an opening of the at least one aperture to variably or adjustably limit the cross-sectional area of the laser beam. Thus, the diaphragm may be configured with an iris-like aperture or opening.

The at least one aperture may be configured to move along an optical axis of the aperture and/or in a plane perpendicular to the optical axis of the aperture so as to variably or adjustably limit a cross-sectional area of the laser beam passing through the aperture. For this purpose, the laser processing head may comprise an actuator, for example a motor, for moving the aperture.

The at least one aperture may be configured to move or slide or translate axially and/or radially with respect to the axis of the laser beam and/or with respect to the optical axis of the optical element and/or with respect to the optical axis of the aperture, for example with respect to the propagation direction of the laser beam, to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture. For this purpose, the laser processing head may comprise an actuator, for example a motor, for moving the aperture. Furthermore, the aperture may be configured to be removed from the beam path of the laser processing head by rotation about an axis parallel to its optical axis or pivoting about an axis perpendicular to its optical axis.

The aperture body may include a coolant-based cooling mechanism, such as a water-based cooling mechanism, to remove heat from the aperture body.

The aperture body may include a surface coating configured to increase absorption of a portion of the laser beam when incident upon the aperture body.

The aperture body may include a beam trap configured to trap the portion of the laser beam incident on the aperture body by repeated total internal reflection. The beam trap may be defined within the aperture body.

The aperture body may comprise a reflector and an absorption unit, wherein the reflector may be configured to reflect at least a part of the portion of the laser beam incident to the aperture body, e.g. the second portion of the laser beam, towards the absorption unit, which in turn may be configured to absorb said reflected portion of the laser beam.

The scanning module may be configured to deflect the laser beam in one or two dimensions. The scanning module may be a galvanometer scanner. The scanning module may include one or more mirrors.

The focusing module may comprise an F-Theta lens, for example the optical element of the focusing module may be an F-Theta lens.

The laser processing head may comprise a sensor module comprising one or more sensors configured to sense the laser power of the portion of the laser beam passing through the opening of the aperture and/or to sense the laser power absorbed by the aperture body and/or to sense the laser power of the laser beam entering the laser processing head.

One or more sensors of the sensor module, e.g. a sensor configured to sense the laser power of the portion of the laser beam passing through the opening of the aperture, may be placed or positioned at the opening, e.g. the opening of the nozzle, through which the laser beam exits the laser processing head. One or more sensors of the sensor module, for example a sensor configured to sense laser power of a laser beam entering the laser processing head, may be placed or positioned at the laser entry module.

As previously described, the diaphragm body may have a coolant-based cooling mechanism, such as a water-cooled diaphragm. The sensor module may comprise a temperature sensor for measuring or determining the temperature of the coolant or water in order to determine one or both of the laser power, i.e. the laser power of the portion of the laser beam that passes through the opening of the aperture and the laser power absorbed by the aperture body.

The laser processing head may comprise a safety switch for switching off the laser beam based on the laser power of the portion of the laser beam passing through the opening of the aperture and/or based on the laser power absorbed by the aperture body and/or based on the temperature of the aperture body sensed by the temperature sensor, for example when at least one of the laser power of the portion of the laser beam passing through the opening of the aperture, the laser power absorbed by the aperture body and the sensed temperature is determined to be above a predetermined value or a critical value.

In a second aspect of the present technique, a laser machining system is provided. The laser processing system may comprise a laser processing head according to the first aspect of the present technique and embodiments thereof described herein, and at least one of a laser source module configured to generate a laser beam and a processor for controlling the laser processing head.

The laser source module may comprise or be a fiber laser or a fiber optic disk laser. Fiber lasers typically have a large bounding region. The laser source module may comprise a single mode laser source or a ring mode laser, such as a tunable ring mode (ARM) laser or a multimode laser source. The laser source module may be configured to generate a laser power of 200 watts or more, particularly a laser power of multiple kW (multiple kilowatts), for example a laser beam having a power equal to or greater than 200W, or equal to or greater than 6kW, preferably equal to or greater than 8kW, particularly greater than 10 kW. Thus, the laser source module may comprise or be at least one of: a disc laser, a fiber disc laser, a ring mode fiber laser, a ring mode disc laser, a diode laser, a single mode fiber laser, or a multimode fiber laser.

The laser machining system may further comprise a processor for controlling the laser machining head, in particular at least one of its components, such as the aperture and/or the scanning module, and/or the laser source module and/or at least one of the collimating module and the focusing module to adjust the focal position of the laser beam.

The processor may be configured to control the laser source module to adjust the laser power of the laser beam, for example in dependence on a sensed or determined laser power of a portion of the laser beam passing through the opening of the aperture, and/or in dependence on a sensed laser power absorbed by the aperture body, and/or in dependence on a sensed temperature of the aperture (or coolant of the aperture), and/or in dependence on a scanning position of the laser beam deflected by the scanning module.

The processor may be configured to control the aperture, e.g. to control the position of the aperture and/or the diameter of its opening. The processor may be configured to control the aperture to adjust or change the cross-sectional area of the laser beam passing through the aperture, for example in dependence on a sensed or determined laser power of a portion of the laser beam passing through the aperture opening, and/or in dependence on a sensed laser power absorbed by the aperture body, and/or in dependence on a sensed temperature of the aperture (or coolant of the aperture), and/or in dependence on a scanning position of the laser beam deflected by the scanning module. The processor may be configured to control the position of the aperture and/or the diameter of its opening, for example, in dependence on a sensed or determined laser power of the portion of the laser beam passing through the aperture of the aperture, and/or in dependence on a sensed laser power absorbed by the aperture body, and/or in dependence on a sensed temperature of the aperture (or coolant of the aperture), and/or in dependence on a scanning position of the laser beam deflected by the scanning module. The processor may be configured to control the aperture to limit a diameter or cross-sectional area of the laser beam passing through the aperture only when the scan module deflects the laser beam within a predefined area at the scan field edge and/or toward the peripheral edge of the optical element.

The processor may be configured to control the safety switch in dependence on a sensed or determined laser power of the portion of the laser beam that passes through the opening of the diaphragm, and/or in dependence on a sensed laser power absorbed by the diaphragm body, and/or in dependence on a sensed temperature of the diaphragm (or coolant of the diaphragm).

In a third aspect of the present technique, a method is provided for controlling a laser processing head to increase a scan field of a laser beam. The method may be used with a laser machining head according to the first aspect of the present technique or with a laser machining system according to the second aspect of the present technique. In this method, a laser beam is introduced into a laser entry module, then the laser beam is collimated by a collimation module, then the laser beam is deflected by a scanning module, and finally the laser beam is focused by a focusing module on, for example, a workpiece. By passing the laser beam through the aperture before the laser beam is focused or in the beam path of the laser processing head between the laser entry module and the focusing module, the cross-sectional area of the laser beam is limited by the aperture body. In other words, a first portion of the cross-sectional area of the laser beam passes through the opening, while a second portion of the cross-sectional area of the laser beam is blocked by the aperture body.

In this method, the cross-sectional area of the laser beam limited by the aperture body may be changed or adjusted, for example the cross-sectional area of the first portion of the laser beam may be increased or decreased.

In this method, the aperture may be controlled to change or adjust the cross-sectional area of the laser beam passing through the aperture. For example, the aperture may be controlled to change or adjust, i.e. increase or decrease, the cross-sectional area or diameter of the opening of the at least one aperture to change or adjust the cross-sectional area of the laser beam passing through the aperture. Alternatively or additionally, at least one aperture may be moved along or parallel to the optical axis of the aperture and/or in a plane perpendicular to the optical axis of the aperture to change or adjust the cross-sectional area of the laser beam passing through the aperture.

In this method, the aperture can be controlled to limit the diameter or cross-sectional area of the laser beam passing through the aperture when (or only when) the scan module deflects the laser beam within a predefined area at the scan field edge and/or deflects the laser beam toward the outer peripheral edge of the optical element.

In the method, the laser power of the laser beam may be adjusted by controlling the laser source module according to the sensed or determined laser power of the portion of the laser beam passing through the opening of the aperture and/or according to the sensed laser power absorbed by the aperture body. Furthermore, the laser source module may be controlled to increase the laser power of the laser beam when the diameter or cross-sectional area of the laser beam is limited by the aperture and/or when the scanning module deflects the laser beam within a predefined area at the edge of the scan field and/or towards the peripheral edge of the optical element.

In the method, the aperture may be controlled to adjust or change the cross-sectional area of the laser beam passing through the aperture, for example in dependence on a sensed or determined laser power of the portion of the laser beam passing through the aperture opening and/or in dependence on a sensed laser power absorbed by the aperture body.

In the method, one or both of a laser power of a portion of the laser beam passing through the opening of the diaphragm and a laser power absorbed by the diaphragm body may be determined or sensed by the sensor module.

In the method, a safety switch may be controlled to turn off the laser source module, in particular when a temperature is sensed, e.g. the temperature of an aperture exceeds a threshold or critical value.

Drawings

Unless otherwise indicated, any reference to "radial," "radially," "circumferential," "circumferentially," and similar terms should be understood with reference to the central axis of the referenced component.

The above-mentioned attributes and other features and advantages of the present technology, and the manner of attaining them, will become more apparent and the present technology itself will be better understood by reference to the following description of embodiments of the present technology taken in conjunction with the accompanying drawings, wherein:

FIG. 1 schematically illustrates a simplified exemplary embodiment of a laser processing system having a laser processing head of the present technology, in which at least one aperture of the present technology is incorporated;

FIGS. 2A and 2B schematically illustrate the function of an exemplary embodiment of at least one aperture;

FIGS. 3A, 3B, and 3C schematically illustrate the increased scan field of the laser beam by the at least one aperture as compared to the laser beam projected without the at least one aperture;

FIG. 4 schematically illustrates an exemplary embodiment in which the aperture body blocks only a portion of the entire edge of the laser beam;

FIG. 5 schematically illustrates an exemplary embodiment in which at least one aperture adjusts the cross-sectional area of the aperture opening to adjustably limit the cross-sectional area of the laser beam passing through the aperture;

FIG. 6 schematically illustrates an exemplary embodiment in which at least one aperture is movable parallel to the optical axis of the aperture to adjustably limit the cross-sectional area of the laser beam passing through the aperture;

FIG. 7 schematically illustrates an exemplary embodiment in which at least one aperture is movable in a plane perpendicular to the optical axis of the aperture to adjustably limit the cross-sectional area of a laser beam passing through the aperture;

FIG. 8 schematically illustrates one exemplary embodiment of at least one aperture having a plurality of apertures to sequentially limit the cross-sectional area of a laser beam passing through the apertures;

FIG. 9 schematically illustrates an exemplary embodiment of at least one aperture having a coolant-based cooling mechanism;

FIG. 10A schematically illustrates one exemplary embodiment of at least one aperture;

FIG. 10B schematically illustrates an exemplary embodiment of at least one aperture having a surface coating;

FIG. 11 schematically illustrates an exemplary embodiment of at least one aperture with a beam trap; and

FIG. 12 schematically illustrates an exemplary embodiment of at least one aperture having a reflector and an absorbing unit, in accordance with aspects of the present technique.

Detailed Description

Hereinafter, the above and other features of the present technology will be described in detail. Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to the same or similar elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It should be noted that the illustrated embodiments illustrate rather than limit the invention. It may be evident that such embodiment(s) may be practiced without these specific details.

Fig. 1 shows a laser machining system 2 with a laser machining head 1, for example a laser cutting head or a laser welding head, in which at least one aperture 100 according to the present technique is incorporated.

The laser machining system 2 may be any system for transmitting or irradiating a laser beam to a target surface or a workpiece W. The laser machining system 2 may be, but is not limited to, one of a laser cutting system, a laser engraving system, a laser ablation system, a laser drilling system, a laser beam machining system, a laser beam welding system, a laser hybrid welding system, a laser welding system, an additive manufacturing system using a laser, such as a laser printing system, a laser cladding system, and the like.

The laser machining system 2 may comprise a laser beam generating source or laser source module 42 for generating a laser beam 9, and the laser machining head 1. The laser machining system may optionally include a processor 48.

The laser source module 42 may include a single mode laser source or a multimode laser source. The laser source module 42 may be configured to generate a laser beam having a power of hundreds or more watts, such as 2kW or more, such as 6kW and more or 8kW and more.

The laser processing head 1 may comprise a housing in which components of the laser processing head 1, for example optical elements for guiding the laser beam 9, may be arranged.

The laser processing head 1 comprises a laser entry module 40 for introducing the laser beam 9, a collimation module 44 for collimating the laser beam 9, a scanning module 46 for scanning or deflecting the laser beam 9, and a focusing module 50 for focusing the laser beam 9 on the workpiece W.

The laser beam 9 may be fed to the laser processing head 1 via a laser entry module 40. The laser beam 9 is directed from the laser entry module 40 towards the focusing module 50, thus defining the overall or general direction of transmission of the laser beam 9. It is accordingly understood that the position or optical position of the different components relative to each other, for example the position or positioning of the laser entry module 40, may be understood as an optically upstream position or positioning, while the position or positioning of the focusing module 50 may be understood as an optically downstream position or positioning. Generally, the direction extending from laser entry module 40 to focusing module 50 may be understood as optically downstream, while the direction extending from focusing module 50 to laser entry module 40 may be understood as optically upstream. All directions may be understood as directions along the propagation or travel or transmission of the laser beam from the laser entry module 40 to the focusing module 50. It may be noted that in the embodiment of fig. 1, laser entry module 40, collimation module 44, scanning module 46, and focusing module 50 are arranged linearly, i.e., along a line. However, the embodiment shown in FIG. 1 is for exemplary purposes only, and the present technique is not limited to a linear arrangement of the

modules

40, 44, 46, 50. In other embodiments (not shown), the

modules

40, 44, 46, 50 may be arranged differently, for example the laser entry module 40 and the collimation module 44 may be arranged perpendicular or at an angle to the scanning module 46 and the focusing module 50.

The laser source module 42 may be coupled to the laser entry module 40, for example by fiber optic coupling. The laser beam 9 generated by the laser source module 42 may be fed or introduced or provided to the laser processing head 1 at the laser entry module 40 or via the laser entry module 40. The laser entry module 40 may be, for example, the exit end of an optical fiber (not shown).

The laser beam 9 emitted from the laser entrance module 40 is directed to the collimation module 44. The collimating module 44 may include at least one collimating optical element, such as one or more collimating lenses. The laser beam 9 is collimated by the collimating module 44. The collimated laser beam 9 may then be directed to a scanning module 46.

The scanning module 46 may deflect the laser beam 9 in one or two dimensions. The scanning module 46 may include at least one scanning optical element, such as one or more scanning mirrors.

For positioning the laser beam 9 in two dimensions, either a single mirror arrangement may be used, where the mirror is rotated in two axes, e.g. in two orthogonal axes or in an X-axis and a Y-axis, or a double mirror arrangement with two mirrors at close spacing-each mirror being used for an orthogonal axis to reflect the laser beam in the respective axis. Each of the two mirrors may be driven by a galvanometer or by other actuation means such as an electric motor. For example, the scanning module may be a galvanometer scanner, i.e. the scanning module 46 may have two galvanometers, each with a respective reflector, e.g. a mirror, to deflect the laser beam 9.

The laser beam 9 deflected or positioned or steered by the scanning module 46 is directed to a focusing module 50. The laser beam 9 is focused by the focusing module onto the workpiece W.

The focusing module 50 may include at least one focusing optical element, such as one or more focusing lenses. The focusing module 40 may include an F-Theta lens. In other words, the focusing optics may be an F-Theta lens.

The laser beam 9 may pass through or leave the laser processing head 1 via an outlet or nozzle 58. The nozzle 58 may be located optically downstream of the focusing module 50.

The laser processing head 1 further comprises at least one aperture 100, the aperture 100 being configured to limit the diameter or cross-sectional area of the laser beam passing through the aperture to increase the scan field of the laser beam 9. The structure and function of the diaphragm 100 have been described later with reference to fig. 2A and 2B, and the increase in the scanning field has been described later with reference to fig. 3A, 3B, and 3C.

As shown in fig. 1, the at least one aperture 100 may include a first aperture 10 located between the laser entry module 40 and the collimation module 44. The first aperture 10 may limit the cross-sectional area of the laser beam 9 transmitted from the laser entry module 40 to the collimation module 44. The position or location between laser entry module 40 and collimation module 44 may be referred to as a first position.

The at least one aperture 100 may include a second aperture 20 located between the collimation module 44 and the scanning module 46. The second aperture 20 may limit the cross-sectional area of the laser beam 9 transmitted from the collimation module 44 to the scanning module 46. The position or location between collimation module 44 and scanning module 46 may be referred to as a second position. In general, in this position, all the beams in the laser processing head are coaxial. For example, a light beam in a coaxial illumination system or a distance measurement system, such as Optical Coherence Tomography (OCT), conoscope, intensity-based measurement system, etc., may be combined with a laser beam by a beam splitter. Therefore, the second diaphragm 20 can prevent the intensity of these light beams incident on the following optical elements from being excessively high and reduce scattering of light, thereby improving the signal-to-noise ratio or contrast.

The at least one aperture 100 may include a third aperture 30 located between the scanning module 46 and the focusing module 50. The third aperture 30 may limit the cross-sectional area of the laser beam 9 transmitted from the scanning module 46 to the focusing module 50. The position or location between the scanning module 46 and the focusing module 50 may be referred to as a third position.

The at least one aperture 100 may include only one, only two, or all of the first aperture 10, the second aperture 20, and the third aperture 30. For example, the at least one aperture 100 may include only the first aperture or only the second aperture 20, or only the third aperture 30, or only the first aperture 10 and the second aperture 20, or only the first aperture 10 and the third aperture 30, or only the second aperture 20 and the third aperture 30, or all of the first aperture 10, the second aperture 20, and the third aperture 30.

Typically, at least one aperture 100 is located optically downstream of the laser entry module 40 and optically upstream of the focusing module 50.

Hereinafter, the structure and function of an exemplary embodiment of at least one diaphragm 100 will be described with reference to fig. 2A and 2B, fig. 3A to 3C, and fig. 10A.

As shown in fig. 10A, the first diaphragm 10 includes a first diaphragm body 14 and an opening 12 of the first diaphragm. The second diaphragm 20 includes a second diaphragm body 24 and an opening 22 of the second diaphragm. The third diaphragm 30 includes a third diaphragm body 34 and an opening 32 of the third diaphragm. The first, second and/or

third diaphragm

10, 20, 30 is denoted as diaphragm 100 in the following. The description provided in relation to the aperture 100 also applies to the first, second and

third apertures

10, 20, 30. The diaphragm 100 includes a diaphragm body 104 and an opening 102. The diaphragm 100 may have an annular shape with a diaphragm body 104 defining an opening 102. The diaphragm body 104 may have a planar shape, for example, a disk shape. Typically, the at least one aperture 100 is located optically downstream of the laser entry module 40 and optically upstream of the focusing module 50, in other words, the at least one aperture 100 is optically between the laser entry module 40 and the focusing module 50.

As previously mentioned, the focusing module 50 may include at least one focusing optical element, such as one or more focusing lenses. Similarly, the collimating module 44 may include at least one collimating optical element, such as one or more collimating lenses. Furthermore, the scanning module may comprise at least one scanning optical element, for example one or more scanning mirrors. The focusing optics and/or collimating optics and/or scanning optics may be generally referred to as optics 52.

Fig. 2A illustrates the function of the aperture 100, and the aperture 100 may be, for example, a third aperture 30 located between the scanning module 46 and the focusing module 50.

Typically, the aperture 100 is located upstream of the optical element 52, such as upstream of an F-theta lens used as the focusing optical element 52. The arrow 9x shows the direction of propagation or travel of the laser beam 9. The aperture 100 and the optical element 52 may be arranged spaced apart from each other, i.e. may not be in contact with each other.

The diaphragm 100 restricts the cross-sectional area 9c of the laser beam 9 by the diaphragm body 104. In other words, the aperture 100 is sized and positioned to allow the first portion 91 of the laser beam 9 to pass through the opening 102 while blocking the second portion 92 of the laser beam 9 by the aperture body 104. The blocking may be performed by physically blocking the light beam, and for this reason, at least a part of the diaphragm body 104 may be arranged in a traveling path or a propagation path of the laser beam 9. In other words, the cross-sectional area 9c of the laser beam 9 is divided or split or cleaved by the aperture 100 into a cross-sectional area of the laser beam defining a first part 91 of the laser beam 9 and a cross-sectional area of the laser beam defining a second part 92 of the laser beam 9, the first part 91 of the laser beam 9 being allowed to travel through the opening 102 towards the downstream side of the aperture 100, the second part 92 of the laser beam 9 being blocked or stopped by the aperture body 104 on the upstream side of the aperture 100. In short, a part of the laser beam 9, i.e., the second part 92 of the laser beam 9 is blocked by the diaphragm body 104 and cannot be propagated or transmitted toward the optical element 52.

Briefly, as shown in FIG. 2A, the aperture 100 limits the cross-sectional area of the laser beam 9. Explained further, the cross-sectional area of the laser beam passing through the aperture 100, i.e. the cross-sectional area 91c of the first portion 91 of the laser beam 9, is smaller than the cross-sectional area 9c of the laser beam 9 upstream of the aperture 100, i.e. the laser beam 9 received at the aperture 100.

In other words, as shown in fig. 2A, the aperture 100 limits the diameter of the laser beam 9. Explained further, the diameter of the laser beam passing through the aperture 100, i.e. the diameter 91d of the first portion 91 of the laser beam 9, is smaller than the diameter 9d of the laser beam 9 upstream of the aperture 100, i.e. the laser beam 9 received at the aperture 100.

In other words, as shown in fig. 2A, the diaphragm 100 restricts the outer periphery 9p of the laser beam 9. Explained further, the outer periphery or edge of the laser beam passing through the aperture 100, i.e. the outer periphery 91p of the first portion 91 of the laser beam 9, is smaller than the outer periphery 9p of the laser beam 9 upstream of the aperture 100, i.e. the laser beam 9 received at the aperture 100.

It may be noted that although fig. 2A and some other figures show the optical axis 100x of the aperture 100 to coincide with or be coaxial with the optical axis 52x of the optical element 52, the aperture 100 may be arranged such that the optical axis 100x of the aperture 100 may not coincide with the optical axis 52x of the optical element 52, e.g. the optical axis 100x of the aperture 100 may be arranged parallel to the optical axis 52x of the optical element 52 and spaced apart from the optical axis 52x of the optical element 52, e.g. as shown in fig. 3C.

The aperture 100 may be arranged in the path of the laser beam 9 propagating towards the optical element 52, for example, in the path of the laser beam propagating towards the focusing module 50 after being deflected by the scanning module 46.

The laser processing head 1 may comprise an aperture positioning mechanism (not shown) configured to arrange and remove, i.e. reversibly arrange and remove, an aperture 100 in the path of the laser beam 9 propagating towards the optical element 52. By removing or arranging the aperture 100 in the path of the laser beam 9, beam characteristics, such as power density distribution and beam size, i.e. the width or cross-sectional area of the laser beam 9, can be changed.

The laser processing head 1 may comprise an aperture calibration mechanism (not shown) configured to calibrate, i.e. move, the aperture 100 to calibrate or orient the aperture 100 with respect to the laser beam 9. In other words, with the aperture 100 disposed in the beam path, the laser beam 9 may be incident on a first location of the optical surface 54 of the optical element 52, and then the laser beam 9 may be repositioned to be incident on a second location of the optical surface 54. When the laser beam 9 is repositioned, the aperture calibration mechanism calibrates or repositions the aperture 100 accordingly or correspondingly such that the aperture 100 is repositioned or remains disposed in the beam path of the laser beam 9 traveling toward the optical element 52. The movement of the aperture 100 for repositioning the aperture 100 may be performed simultaneously with the scanning movement of the laser beam 9, i.e. while the laser beam 9 is being repositioned by the scanning module 46.

The aperture calibration mechanism may be configured to move the aperture parallel to or along the optical axis 100x of the aperture 100 and/or parallel to or along the optical axis 52x of the optical element 52 and/or in a plane perpendicular to the optical axis 100x of the aperture 100 and/or perpendicular to the optical axis 52x of the optical element 52 to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture. The variable or adjustable limitation of the cross-sectional area 9c of the laser beam 9 has been explained below with reference to fig. 6 and 7.

Fig. 2B shows the laser beam 9 and a portion of the laser beam 9, i.e. the first portion 91 allowed to pass through the opening 102 and the second portion 92 blocked by the aperture body 104, and their corresponding intensity or power distribution, as shown by curve 80. Curve 80 shows the intensity or power distribution of the laser beam 9 with respect to the radius or radial distance from the central axis of the laser beam 9. Axis 81 shows the radial distance or beam waist 'ω' and axis 82 shows the intensity 'I'. Lines I, II, III and IV are included to show correspondence of a portion of curve 80 or an area under curve 80 to a cross section or portion of laser beam 9, such as first portion 91 and second portion 92.

Curve 80 represents a typical laser beam 9 having a gaussian shaped intensity distribution or an intensity distribution similar to a gaussian shaped intensity distribution. I is ₀ I.e. the maximum provided on the axis 82, describes the maximum of the intensity and the corresponding power. Radial distance omega ₀ I.e. the distance from the central axis of the laser beam 9 shows that the intensity of the beam drops to 1/e of the maximum value ² The distance or radius of (a). As can be seen from FIG. 2B, the intensity of the region of the beam 9 further from the central axis of the beam 9 is further reduced, i.e. less than 1/e ² 。

As can be seen from fig. 2B, the at least one aperture 100 allows the portion of the light beam 9 having a higher intensity or higher power density distribution, e.g. the light beam between lines II and III, to pass through and blocks one or more peripheral portions of the light beam 9, e.g. the light beam between lines I and II and the light beam between lines III and IV, which represent light beams of a lower intensity or lower power density distribution. In short, a portion of the light beam 9 having a relatively low intensity, for example the second portion 92, is blocked by the aperture 100, whereas a portion of the light beam 9 having a relatively high intensity, for example the first portion 91, is allowed to pass through by the aperture 100. More precisely, the portion of the light beam 9 having a relatively low intensity-to-radial distance ratio of the light beam 9, for example the second portion 92, is blocked by the aperture 100, whereas the portion of the light beam 9 having a relatively high intensity-to-radial distance ratio, for example the first portion 91, is allowed to pass through by the aperture 100. In short, the first portion 91 of the laser beam 9 has a greater intensity-to-cross-sectional area ratio than the intensity-to-cross-sectional area ratio of the second portion 92. In brief, the power density profile of the first portion 91 of the laser beam 9 is larger or higher than the power density profile of the second portion 92 of the laser beam 9.

As described above, ω ₀ Is the radial distance from the central axis of the laser beam 9 where the intensity has dropped to 1/e ² I.e. about 13.5%. Beyond radius omega ₀ Or energy other than it, e.g. the energy of the laser beam 9 in the region between lines I and II and between lines III and IV, may be high enough to heat and destroy the structure, but too low or too little for processing. Thus, the aperture 100 causes the first portion 91 of the laser beam 9 to be centered from the laser beam 9The shaft extending to a radial distance ω ₀ And the second portion 92 of the laser beam 9 extends beyond the radial distance ω ₀ Or extend radially outwardly thereof.

In other words, the aperture 100 may be configured, i.e., positioned and/or oriented and/or sized, such that a laser beam passing through the aperture 100 has 1/e of the width or radius of the laser beam 9 received at the aperture ² . In other words, the diameter 91d or radius of the first portion 91 of the laser beam 9 is 1/e of the diameter 9d or radius of the laser beam 9 upstream of the aperture 100 ² 。

The at least one aperture 100 may be configured such that the intensity of the laser beam optically exiting downstream thereof is between 75% and 90%, preferably between 85% and 87%, more preferably about 86.5% of the total intensity of the laser beam received at the at least one aperture.

When the at least one aperture 100 includes at least two of the first, second and

third apertures

10, 20, 30, the cross-sectional areas of the openings of the first, second and

third apertures

10, 20 and 20 may be such that the intensity of the laser beam exiting from the most downstream aperture 100 is between 75% and 90%, preferably between 85% and 87%, more preferably about 86.5% of the total intensity of the laser beam 9 received at the most upstream aperture 100.

For ease of understanding, fig. 3A shows a laser beam 9 having a central axis 99x, the cross-sectional area of which is not limited by the aperture 100. As can be seen from fig. 3A, a portion of the laser beam at the periphery 9p of the laser beam falls at and beyond the edges of the optical surface 54, and thus may undesirably deposit energy into the structures or features of the edge or adjacent optical element 52, e.g., the lens holder (not shown), which may thus lead to adverse effects such as heating of the optical element 52 and/or the adjacent structures or features, e.g., the lens holder. Thus, as shown in FIG. 3B, a scan field S is generally defined that is the maximum recommended navigable area of the central axis 99x of the beam 9 to avoid the outer periphery 9p of the beam 9 falling outside the edges of the optical surface 54 and to avoid associated adverse effects, such as heating, of optical elements and/or adjacent structures or components. Therefore, in the conventional laser processing head, the size of the scanning field S is limited.

However, in the laser processing head 1 of the present technology as shown in fig. 3C, by using the aperture 100, the first part 91 of the laser beam 9 having a larger intensity or power to cross-sectional area ratio is emitted from the laser processing head 1 to perform laser processing, while the second part 92 having a lower intensity or power to cross-sectional area ratio is blocked by the aperture 100. In short, although the beam diameter or the cross-sectional area of the laser beam 9 supplied to the workpiece via the optical element 52 is small as compared with those in fig. 3A and 3B, the intensity thereof is still sufficient for laser processing. As the beam diameter decreases, the size or area of the scan field S of the beam 9 may increase. In short, central axis 99x of beam 9 may be positioned closer to the edge of optical surface 54 by scanning module 46 without the outer perimeter 9p of beam 9 extending beyond the edge of optical surface 54.

As shown in fig. 2A, the at least one aperture 100 may be configured, i.e., sized or positioned and/or oriented, e.g., relative to the focusing module 50 or the collimating module 44 or the scanning module 46, such that the entire cross-sectional area of the laser beam passing through the opening 102 of the aperture 100, or the outer perimeter 91p of the entire cross-sectional area 91c of the laser beam 91, is incident on or transmitted through the optical surface 54 of the optical element 52.

As shown in fig. 2A, the aperture 100 may be configured, i.e., sized or positioned and/or oriented, such that the entire edge or periphery 9p of the laser beam 9 is blocked by the aperture body 104. Alternatively, as shown in fig. 4, the aperture 100 may be configured, i.e., sized or positioned and/or oriented, such that the entire edge or only a portion of the outer perimeter 9p of the laser beam 9 is blocked by the aperture body 104.

It may be noted that the opening 102 of the aperture 100 may be smaller than the aperture of the optical element 52, for example, smaller than the aperture of an F-theta lens. However, the function of the diaphragm 100 explained with reference to fig. 2B may also be realized by the diaphragm 100 having the opening 102 not smaller than the aperture of the optical element 52, wherein the diaphragm 100 is positioned such that at least a part of the laser beam 9 is blocked by the diaphragm body 104.

It is also noted that although the aperture 100 is described as having one aperture 100 at one location, at least one aperture 100 may include a plurality of

apertures

100a, 100b, as shown in fig. 8, which in turn limit the cross-sectional area 9c of the laser beam 9, as shown in fig. 8. The plurality of

apertures

100a, 100b may include an upstream aperture 100a and a downstream aperture 100b relative to the optical element 52 and the direction 9 x. The aperture 102a of the upstream diaphragm 100a may be smaller than the aperture 102b of the downstream diaphragm 100 b. The plurality of

apertures

100a, 100b may be movable relative to each other and/or relative to the optical element 52 in a direction parallel to or along the optical axis 100x of the aperture 100 and/or parallel to or along the optical axis 52x of the optical element 52, and/or in a plane perpendicular to the optical axis 100x of the aperture 100 and/or perpendicular to the optical axis 52 of the optical element 52, to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture 100.

One or more of each of the first, second and

third apertures

10, 20, 30 may comprise an upstream aperture 100a and a downstream aperture 100b, as explained above.

The at least one aperture 100 may be configured to adjustably or variably restrict the cross-sectional area of the laser beam passing through the aperture, i.e. to vary the cross-sectional area 91c of the first portion 91 of the laser beam 9. Fig. 5 schematically illustrates an exemplary embodiment in which at least one aperture 100 adjusts or changes the cross-sectional area 102c of the opening 102 of the aperture 100 and thus the cross-sectional area of the laser beam passing therethrough. The diaphragm body 104 may be formed as a mechanical diaphragm or a mechanical shutter that can be moved in a radial back and forth direction to change the cross-sectional area 102c of the opening or the radius or diameter of the opening 102. Thus, the cross-sectional area may change the cross-sectional area 91c or the diameter 91d of the first portion 91 of the laser beam 9 passing through the opening. In other words, the proportions of the first portion 91 of the laser beam 9 and the second portion 92 of the laser beam 9 may be varied by radially increasing or decreasing the aperture 102 of the aperture 100. More specifically, the ratio of the cross-sectional area 91c of the first portion 91 of the laser beam 9 to the cross-sectional area 92c of the second portion 92 of the laser beam 9 may be varied by radially increasing or decreasing the opening 102 of the aperture 100. The diaphragm body 104 may be moved to radially increase or decrease the opening 102 of the diaphragm 100 by using an actuator such as a motor (not shown).

Fig. 6 schematically illustrates an exemplary embodiment in which at least one aperture 100 is movable parallel to or along the optical axis 100x of the aperture 100 to adjustably limit the cross-sectional area of the laser beam passing through the aperture. As can be seen in fig. 6, the distances D1, D2 between the aperture 100 and the optical surface 54 may be increased or decreased, such as an aperture calibration mechanism (not shown) as described above. Thus, as shown in fig. 6, the at least one aperture 100 may be configured to adjustably or variably restrict the cross-sectional area of the laser beam passing through the aperture, i.e., to vary the cross-sectional area 91c of the first portion 91 of the laser beam. The diaphragm body 104 can be moved in the axial back and forth direction to change the cross-sectional area 91c of the first portion 91 of the laser beam 9. Thus, the cross-sectional area 91c or the diameter 91d of the laser beam 9 passing through the first portion 91 of the aperture can be changed. In other words, the proportions of the first portion 91 of the laser beam 9 and the second portion 92 of the laser beam 9 may be changed by axially increasing or decreasing the distances D1, D2 of the aperture 100 from the optical surface 54 or the optical element 52 or the focusing module 50 or the scanning module 46 or the collimating module 44. More particularly, the ratio of the cross-sectional area 91c of the first portion 91 of the laser beam 9 to the cross-sectional area 92c of the second portion of the laser beam 9 can be varied by axially increasing or decreasing the distance D1, D2 of the aperture 100 from the optical surface 54. The diaphragm body 104 may be moved axially using a diaphragm alignment mechanism, which may use an actuator (not shown) such as a motor.

Fig. 7 schematically illustrates an exemplary embodiment in which at least one aperture 100 is movable in a plane perpendicular to the optical axis 100x of the aperture 100 to adjustably limit the cross-sectional area of the laser beam passing through the aperture, as can be seen from a comparison of (a) and (b) in fig. 7 between the optical axis 100x of the aperture 100 and the optical axis 52x of the optical element 52. As can be seen in fig. 7, the lateral or horizontal distance or radial distance between the optical axis 100x of the aperture 100 and the optical axis 52x of the optical surface 54 may be increased or decreased, for example, an aperture calibration mechanism (not shown).

It may be noted that the aperture calibration mechanism may be configured to simultaneously move the aperture 100 along or parallel to the optical axis 100x of the aperture 100 and/or along or parallel to the optical axis 52x of the optical element 52 and/or move the aperture 100 in a plane perpendicular to the optical axis 100x of the aperture 100 and/or in a plane perpendicular to the optical axis 52x of the optical element 52 to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture.

In the following, various exemplary embodiments of the diaphragm 100 are explained with reference to fig. 9-12.

Fig. 9 schematically illustrates an exemplary embodiment of at least one aperture having a coolant based cooling mechanism 70. Preferably, the aperture with the cooling mechanism may be stationary, i.e. immovable. In this case, the cooling mechanism can be designed to be considerably simpler than the cooling mechanism for the moving element. The coolant based cooling mechanism 70 includes a coolant 71, the coolant 71 flowing through a cooling channel or coolant flow channel 72 or coolant flow path 72. The coolant flow channel 72 may be in surface contact with at least a portion of the surface of the diaphragm body 104. Preferably, the coolant flow passage 72 is arranged at a surface of the diaphragm body 104 facing the optical downstream direction, in other words, at a surface opposite to the surface where the laser beam 9 is blocked. The coolant 71 enters the coolant flow passage 72 through the inlet 72a of the coolant flow passage 72, flows through the coolant flow passage 72, performs heat exchange or cooling of the diaphragm body 104 while flowing through the coolant flow passage 72, and flows out of the coolant flow passage 72 through the outlet 72b of the coolant flow passage 72. The coolant 71 may be water. The coolant-based cooling mechanism 70 removes heat from the aperture body 104, such as heat taken by the aperture body 104 from the second portion 92 of the laser beam blocked by the aperture body 104.

Fig. 10B schematically illustrates an exemplary embodiment of at least one aperture 100 having a surface coating 73. A surface coating 73 may be applied to at least one surface of the iris body 104. Preferably, the surface coating 73 may be arranged at a surface of the diaphragm body 104 facing the optical upstream direction, in other words, at a surface on which the laser beam 9 is blocked or incident. The surface coating 73 serves to absorb the incident laser beam, i.e. the second part 92 of the laser beam 9, in order to avoid undesired reflections or scattering of the laser power after incidence on the aperture body 104.

Fig. 11 schematically shows an exemplary embodiment of at least one aperture 100 with a beam trap 74. The beam trap 74 may be formed within the aperture body 104. Preferably, the beam trap 74 may be arranged at the surface of the diaphragm body 104 facing the optical upstream direction, in other words, at the surface where the laser beam 9 is blocked. The beam trap 74 functions to absorb the incident laser beam 9 by subjecting it, i.e. at least a part of the second portion 92 of the laser beam 9, to repeated total internal reflection, thus avoiding undesired reflections or scattering. It may be noted that the depiction of fig. 11 shows an exploded view of aperture 100 for ease of understanding total internal reflection.

Fig. 12 schematically shows an exemplary embodiment of at least one aperture 100 with a reflector 76 and an absorption unit 78. The reflector 76, which may be a mirror, may be formed on or at a surface of the aperture body 104, for example in the form of a reflective coating. Thus, the reflector 76 may have the shape of a circular mirror with a hole in the center. Preferably, the reflector 76 may be disposed on a surface of the diaphragm body 104 facing the optical upstream direction, i.e., a surface on which the laser beam 9 is blocked or incident. The reflector 76 is used to reflect the incident laser beam, i.e. at least a part of the second portion 92 of the laser beam 9, towards the absorption unit 78. The absorption unit 78 may be arranged to receive a reflected portion of the laser beam and to absorb the incident laser beam 9, thereby avoiding undesired reflection or scattering of the laser power after incidence on the aperture body 104. The absorption unit 78 may be actively cooled, for example, by using a coolant-based cooling mechanism, similar to the coolant-based cooling mechanism 70 described above. Thus, the position where the laser power is absorbed may be far from the blocking surface, i.e. from the reflector.

As shown in fig. 1, the laser processing head 1 may comprise a sensor module 60, the sensor module 60 comprising one or more sensors 61 configured to sense a laser power of a portion, e.g. the first portion 91, of the laser beam 9 passing through the opening 102 of the aperture 100 and/or to sense a laser power absorbed by the aperture body 104. The laser sensor module 60 may include one or more sensors 62 configured to sense the laser power of the laser beam 9 upstream of the aperture 100. The sensor configured to sense the laser power of the portion of the laser beam 9 passing through the opening 102 of the aperture 100, i.e. the first portion 91, may be positioned or located at the nozzle 58 of the laser processing head 1, in particular at the opening of the nozzle 58, more in particular outside or downstream of the opening of the nozzle 58 of the laser processing head 1.

As previously described with reference to fig. 9, the iris body 104 may have a coolant-based cooling mechanism 70. The sensor module 60 may include a temperature sensor 63, such as a first temperature sensor 63, disposed at the inlet 72a of the coolant flow channel 72 to measure or determine the temperature of the coolant 71 entering the coolant flow channel 72. The sensor module 60 may include a temperature sensor 64, such as a second temperature sensor 64, disposed at the outlet 72b of the coolant flow passage 72 to measure or determine the temperature of the coolant 71 exiting the coolant flow passage 72.

One or more sensors 61, 62 of the sensor module 60 may be in communication with the processor 48 of the laser processing head 1 or the system 2.

One or more sensors 63, 64 of the sensor module 60 may be in communication with the processor 48 of the laser processing head 1. From the temperature difference sensed by the temperature sensors 63, 64, the processor 48 may determine the laser power of a portion of the laser beam 9 passing through the opening 102 of the aperture 100, e.g. the first portion 91, and/or sense the laser power absorbed by the aperture body 104.

The processor 48 may be configured to control the laser source module 42 to adjust the laser power of the laser beam 9 generated by the laser source module 42.

The processor 48 may be configured to control the aperture 100 to adjust or change the cross-sectional area of the laser beam passing through the aperture 100, e.g. in dependence on a sensed or determined laser power of a portion, e.g. the first portion 91, of the opening 102 of the laser beam 9 passing through the aperture 100 and/or in dependence on a sensed laser power absorbed by the aperture body 104 and/or in dependence on a scanning position of the laser beam deflected by the scanning module.

The processor 48 may control the aperture body 104 or a corresponding actuator to change or adjust the cross-sectional area 102c of the opening 102 of at least one aperture 100 to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture, as explained with reference to fig. 5.

The processor 48 may control the aperture body 104 or a corresponding calibration mechanism or actuator to move the aperture 100 along or parallel to the optical axis 100x of the aperture 100 and/or along or parallel to the optical axis 52x of the aperture 100 and/or in a plane perpendicular to the optical axis 100x of the aperture 100 and/or in a plane perpendicular to the optical axis 52x of the optical element 52, for example, to variably or adjustably limit the cross-sectional area of the laser beam passing through the aperture, as explained with reference to fig. 6 and 7, depending on the scanning position of the laser beam deflected by the scanning module.

In a third aspect of the present technique, a method for increasing the scan field S of the laser beam 9 is provided. The method may be used for a laser processing head 1 or a laser processing system 2 as explained above with reference to fig. 1 to 12. In this method, a laser beam 9 is introduced into a laser entry module 40, then the laser beam 9 is collimated by a collimation module 44, then the laser beam 9 is deflected by a scanning module 46, and finally the laser beam 9 is focused by a focusing module 50 on, for example, a workpiece W. In this method, the cross-sectional area 9c of the laser beam 9 is limited by the aperture body 104 by passing the laser beam 9 through the aperture 100, as explained above with reference to fig. 1 to 12.

In the present technique, when a multimode laser is used, some or all of the higher transverse modes can be cut off by the aperture body 104 by inserting the aperture 100 between the collimating module 44 and the laser entry module 40. The remaining laser beam can be focused to a smaller focal diameter because the beam parameter product remains constant. The inserted iris 100 may function like an optical fiber having a small fiber diameter.

Therefore, the beam quality of the laser light can be adjusted by inserting or moving the aperture 100 along the optical axis between the collimating module and the laser light entering module. Thus, a single laser processing head or system may be used to perform both the joining tasks that require high laser power but less demanding for lateral extension of the joint, as well as tasks that require a very small focal diameter to perform the most accurate processing. The beam quality can be switched or changed during processing to change the focus size. Furthermore, laser beam sources with relatively low spatial beam quality, such as diode lasers or multimode fiber lasers, can be used with small compact scan modules while maintaining good processing quality.

In the present technology, the diaphragm 100 may also be understood as a housing opening or a diaphragm.

While the present technology has been described in detail with reference to certain embodiments, it should be understood that the present technology is not limited to those precise embodiments. On the contrary, many modifications and variations will be apparent to those skilled in the art in light of the present disclosure describing exemplary modes for practicing the invention without departing from the scope of the appended claims. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description.

List of reference numerals

1 laser machining head 70 Coolant-based Cooling mechanism

2 laser processing system 71 coolant

9 flow path of coolant for laser beam 72

9d diameter 72a of laser beam inlet of flow path of coolant

9c cross-sectional area 72b of the laser beam outlet of the flow path of the coolant

Peripheral 73 surface coating of 9p laser beam

9x direction of travel of laser beam 74 Beam trap

10 first aperture 76 reflector

12 first aperture opening 78 absorbing unit

14 first diaphragm body 91 first part of the laser beam

20 diameter of first portion of second diaphragm 91d

22 cross-sectional area of a first portion of the opening 91c of the second diaphragm

24 outer periphery of the first portion of the second diaphragm body 91p

30 second portion of laser beam of third aperture 92

Cross-sectional area of second portion of opening 92c of 32 third diaphragm

34 center axis of third diaphragm body 99x laser beam

40 laser entry module 100 aperture

42 laser source module 100a upstream aperture

44 collimating Module 100b downstream Aperture

Optical axis of 46 scanning module 100x aperture

48 processor 102 opening

50 aperture of the upstream diaphragm of the focusing module 102a

52 opening of the diaphragm downstream of the optical element 102b

Cross-sectional area of 52x optical element axis 102c opening

54 optical surface 104 aperture body of optical element

Scanning area of peripheral S laser beam of 54p optical surface

58 nozzles D1, D2 distance

60 sensor module

61. 62 sensor

63. 64 temperature sensor

Claims

1. A laser machining head (1) comprising:

-a laser entry module (40) for introducing a laser beam (9);

-a collimation module (44) configured to be able to collimate the laser beam (9);

-a scanning module (46) configured to be able to deflect the laser beam (9); and

-a focusing module (50) configured to be able to focus the laser beam (9),

characterized in that the laser processing head has

-at least one aperture (100) for increasing the scanning field (S) of the laser beam (9),

wherein the aperture (100) comprises an aperture body (104) and an opening (102), the aperture being configured to enable a cross-sectional area of the laser beam (9) to be limited by the aperture body (104); and

the at least one aperture (100) is located between the laser entry module (40) and the focusing module (50).

2. Laser machining head (1) according to claim 1, characterized in that the at least one aperture (100) is positioned such that the entire cross-sectional area of the laser beam passing through the opening (102) of the aperture (100) is incident on the optical surface (54) of an optical element (52), wherein the optical element (52) is comprised in at least one of the collimation module (44), the scanning module (46) and the focusing module (50).

3. Laser machining head (1) according to claim 1 or 2, characterized in that the aperture body (104) is arranged to block the entire edge (9p) of the laser beam (9) or to block only a part of the entire edge (9p) of the laser beam (9).

4. Laser machining head (1) according to any one of claims 1 to 3, characterized in that the opening (102) of the aperture (100) is smaller than the aperture of the focusing module (50).

5. Laser machining head (1) according to any of claims 1 to 4, characterized in that said at least one aperture (100) comprises at least one of the following:

-a first aperture (10) located between the laser entry module (40) and the collimation module (44) and configured to be able to limit the cross-sectional area of the laser beam (9) propagating from the laser entry module (40) to the collimation module (44);

-a second aperture (20) located between the collimation module (44) and the scanning module (46) and configured to be able to limit the cross-sectional area of the laser beam (9) propagating from the collimation module (44) to the scanning module (46); and

-a third aperture (30) located between the scanning module (46) and the focusing module (50) and configured to be able to limit the cross-sectional area of the laser beam (9) propagating from the scanning module (46) to the focusing module (50).

6. The laser machining head (1) according to any one of claims 1 to 5, characterized in that the at least one aperture (100) is configured such that the width of the laser beam passing through the aperture (100) is less than 95% of the width of the laser beam (9) received at the aperture (100).

7. Laser machining head (1) according to any one of claims 1 to 6, characterized in that said at least one aperture (100) is configured so as to be able to adjustably limit the cross-sectional area of the laser beam passing through it.

8. The laser machining head (1) according to claim 7, characterized in that the at least one aperture (100) is configured to enable adjustment of the cross-sectional area of the opening (102) to adjustably limit the cross-sectional area of the laser beam passing through the aperture.

9. The laser machining head (1) according to claim 7 or 8, characterized in that the at least one aperture (100) is configured to be movable along an optical axis (100x) of the aperture (100) and/or in a plane perpendicular to the optical axis (100x) of the aperture (100) to adjustably limit a cross-sectional area of a laser beam passing through the aperture.

10. Laser machining head (1) according to any one of claims 1 to 9,

the aperture body (104) including a coolant-based cooling mechanism (70) to remove heat from the aperture body (104); and/or

The aperture body (104) comprising a surface coating (73), the surface coating (73) being configured to enable increased absorption of a second portion (92) of the laser beam incident on the aperture body (104); and/or

The aperture body (104) comprising a beam trap (74), the beam trap (74) configured to capture a second portion (92) of the laser beam incident on the aperture body (104) by repeated total internal reflection; and/or

The aperture body (104) includes a reflector (76) and an absorption unit (78), the reflector (76) being arranged to be able to reflect a second portion (92) of the laser beam incident on the aperture body (104) toward the absorption unit (78) for absorbing a reflected portion of the second portion of the laser beam.

11. The laser machining head (1) according to any one of claims 1 to 10, characterized in that it further has a sensor module (60) comprising one or more sensors (61, 62, 63, 64) configured to be able to sense the laser power of the first portion of the laser beam passing through the opening (102) of the aperture (100) and/or to sense the laser power absorbed by the aperture body (104).

12. Laser machining system (2), characterized in that it comprises a laser machining head (1) according to any one of the preceding claims, and a laser source module (42) configured to be able to generate a laser beam (9).

13. The laser processing system (2) of claim 12, wherein the laser source module (42) comprises at least one of a single mode laser source, a multi-mode laser source, or a ring mode laser source.

14. The laser processing system (2) of claim 12 or 13, wherein the laser source module (42) comprises at least one of a disc laser, a fiber disc laser, a ring mode fiber laser, a ring mode disc laser, a diode laser, a single mode fiber laser, or a multimode fiber laser.

15. The laser processing system (2) according to claim 12 or 13, wherein the laser source module (42) is configured to be able to generate a laser beam having a power of at least 200W, or at least 6kW, or at least 8kW, or at least 10 kW.

16. The laser machining system (2) according to any one of claims 12 to 15, further comprising a processor configured to:

-controlling the laser source module (42) to adjust the laser power of the laser beam (9) in dependence of the sensed laser power of the first portion (91) of the laser beam passing through the opening (102) of the aperture (100) and/or in dependence of the sensed laser power absorbed by the aperture body (104) and/or in dependence of the scanning position of the laser beam deflected by the scanning module; and/or

-controlling the aperture (100) to adjust the cross-sectional area of the laser beam passing through the aperture (100) according to the scanning position of the laser beam deflected by the scanning module.

17. A method for controlling a laser processing head, the method comprising:

-introducing a laser beam (9) at a laser entry module (40) of the laser processing head (1);

-collimating the laser beam (9) by a collimation module (44) of the laser processing head (1);

-deflecting the laser beam (9) by a scanning module (46) of the laser processing head (1); and

-focusing the laser beam (9) by means of a focusing module (50) of the laser processing head (1),

characterized in that the method comprises:

-passing the laser beam (9) through an aperture (100) of the laser processing head (1) such that a scan field (S) of the laser beam (9) is increased by limiting a cross-sectional area of the laser beam (9) with the aperture (100).